Double hung window assemblies generally include a frame, an upper window sash, a lower window sash, a pair of balances, and a pair of jambliners. The jambliners are each attached to a window jamb to guide the movement of the window sashes. Due to the tendency of air, water and other particulate matter to infiltrate the space between the sashes, jambliners have been fabricated to include integral sealing members. One such jambliner is disclosed in U.S. Pat. No. 5,2365,308, in which a carpet-like sealing material is integrally formed on the web portion of the jambliner that interconnects the guideways that receive the sashes. Such a seal can often fail in alleviating the infiltration of air and water.